Combined telegraph and telephone system.



PATENTED JAN. 9, 1906.

O. TURGHI.

COMBINED TELEGRAPH AND TELEPHONE SYSTEM.

APPLICATION FILED APB.15,1903.

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CARLOTURCHI, OF FERRARA, ITALY.

COMBINED TELEGRAPH AND TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Jan. .9, 1906.

Application filed April 15, 1903. Serial No. 152,736-

To (all whont it nuty concern:

Be it known that I, CARLO TUROHI, a subject of the King of Italy, residing at Ferrara, Italy, have invented Improvements in a Combined Telegraph and Telephone System, of which the following is a specification.

The chief advantages atforded by the present improvements as compared with existing apparatus are the following: The ordinary telegraphic instruments and the ordinary telephonic instruments may be employed without alteration for the purposes of this invention. Only one line-wire is necessary. The resistance of the line is increased only by a slight amount, which is almost inappreciable in the case of long lines. Rapid telegraphic systems may be employed. The increase in the electromotive force in the line is but small, and consequently entails but a small increase in the cost of working. All disturbances of the telephonic circuit due to the telegraphic current are entirely eliminated, even where the single-line wire belongs to a telegraphic system comprising a great number of wires running side by side, thus insuring complete secrecy in telegraphing; great ease of application of the apparatus, as it is only necessary to arrange a device (separator) between the telegraph-line and the telephone-station in order to render the installation complete. The improved apparatus can be manufactured and installed at a very low cost.

' The accompanying diagrammatic drawing illustrates the arrangement of a complete telephone-station embodying the improved apparatus.

Linetransformer 1.The telephone-station is connected to the telegraph line Z through a line-transformer 1, which has three windings a (0, b6, 0 c. The windings a a and b b belong to the receiving-telephone, and the third winding 0 0 belongs to the microphone and to the calling-up instrument.

18 indicates the telegraphic station.

Separator 2.-This is the principal part of the improved apparatus. Its object is to allow only the telephonic currents to reach the telephone, while eliminating all other currents. It consists of a closed circuit which receives the telephonic currents and the variable portion of the telegraphic currents through the coil 7) b. This circuit is divided for a certain length into two branches 3 3, which form a differential winding a on a soft-iron core before they are united together. Each branch possesses in general a determined capacity and a determined self-induction. In the various cases which occur in practice the capacity of one or the other branch may become in ,finite and the self-induction of one or the The two difan equal other branch may become mil. ferential windings have usually number of turns.

rlIorZc of operation of the sepamzf0r. hen an alternating current passes through the apparatus, the said current produces in the iron core an alternating magnetic flux which is proportional to the difference between the currents that flow in the two branches. If now the respective ohmic resistances of the two branches are equal to each other, then for a given frequency the capaci ties and the self-inductions of the said branches can be regulated in such a manner as to cause the magnetic flux in the iron core to become nil. Further, when two alternating currents of difierent frequencies 6Y2 are passing throughthe apparatus at one and the same time the constants can be regulated in such a manner as to cause the magnetic flux of the current having the frequency in the core to become at], and then only the current having the frequency 112 will generate a flux different from nil. hen the iron core belongs to a telephone, the latter will react only upon currents having the frequency H2 or having generally a frequency a Z a If the ohmic resistances of the two branches are not exactly equal to each other, which may be the casein practice. only a minimum of the flux will be obtained which can be regulated by the constants of the separator; butsince a flux of a determined amount is requisite for the purpose of causing the telephone-plate to vibrate at all it will be understood that this minimum need only be made equal to the said amount, which practice the telephone will be mute or nonresponsive not only to a single determined or selected frequency, but also to frequencies which are higher or lower than the said determined or selected frequency and which, in fact, lie between rather narrow limits. The range of these frequencies may be termed the zone of non responsiveness. Without going too deep into the theory of the matter the following tentative explanation of the fact may be given here. Assuming that the magnetic flux for a determined frequency has a value equal to zero, then for higher or lower frequencies it will have a positive or negative value; but since a determined amount of flux is required in order to set the telephone-plate in vibration at all the telephone will begin to speak or respond only when the flux has reached the said determined value on the positive or negative side of the zero value. The zone of non-responsiveness therefore lies between the positive and negative determined values of the frequencies at which the telephone begins to speak. This is of great importance, because consequently the separator 2 may also be employed in the case where the current which is to be eliminated has a frequency that varies only by a slight amount or where it is desired to eliminate at one and the same time the effect of several currents which have frequencies of but slightly different amounts. An example of the first case is constituted by a telephone-line wire, which is arranged parallel to a power-transmission wire supplied by a dynamo which does not run with a perfectly constant angular velocity. An example of the second case is constituted by a telephone-line or of a telephone telegraphline situated among a great number of telegraph wires. This case occurs most frequently.

Regulation 0 f the sepami0r.For the purpose of regulating the apparatus the electrical conditions of the one branch may be allowed to remain constant while the electrical conditions of the other branch are varied. The capacity is regulated by pressure, and the selfinduction is regulated by a movable core.

T clap/Lon e-recez'oer 5 .The iron core of the station-telephone receiver .5 is separate from the core of the differential winding of the separator 2, the flux of the core of the separator being received or taken up by a winding 6, which is connected in series with the telephone-receiver 5. This arrangement affords the advantage that no alteration need be made in existing telephones when using them for the purposes of this invention, while it allows of varying the flux at will by providing various windings, which may also be connected in parallel.

JMz'orop/wne 7.-Similarly the microphone 7 may be of the usual type. Its winding is constituted by two coils a a and 0 c of the line-transformer 1.

Calling-up dem'ca-As in other telephone and telegraph apparatus connected to one and the same line, it has been found necessary to dispense with the electromagnetic calling-up device as ordinarily employed, because the latter influences the telegraph apparatus.

The operation of the calling-up device is as follows: The switch 13 closes the circuit of the self-interrupter 9, its vibrations or the current impulses produced by such vibrations being transmitted to the line L through windings 0 c and being taken up at the other station by an electric sounder in series with the line L. This sounder consists of an ordinary telephone whose diaphragm vibrates synchronously with the interrupter. Such a sounder is also provided at the station represented in the drawings and is there shown at 8.

Line-condenser 10.-In telegraphing the current will be momentarily interrupted by each transmission of a character, as will be seen. If at this moment telephoning is taking place on the same line, the electric connections would be interrupted. For this reason the condenser 10 is provided, which serves to close the circuit for a telephonic current at this time. The telephone 5 of the station is utilized by the telephone officials and is connected with the subscribers telephone 17 at the same station by a switchboard 16, switch 14: being employed to cut out the central telephone 5 and cut in the switchboard 16.

The improved apparatus thus allows of transmitting and receiving spoken messages over an existing telegraph-line. For example, in the case of an existing telegraph-wire between two towns when the station operator at one town desires to connect the telephoneswitchboard of his own town to the line he has only to rotate the switch 14 in order to cut his telephone-receiver out of circuit and to transmit the flux of the core of the separator 2 directly to the switchboard. In the case of a subscriber situated at a very great distance it is advisable to intensify the flux received in the core, as described under Telephone-receiver 5. The actual transmission of the spoken words of the subscribers is not quite so simple-namely, the microphone-current of the subscribers instrument after flowing through the separator reaches the wire of the line Z only in a very weak condition; on the other hand, it could not directly reach the line Z unless a second line were provided between the subscribers instrument and the station. This difiiculty is overcome by the employment of a relay 11 of great simplicity. This relay consists of a telephone 12, connected in series with the subscribers instrument. This telephone speaks into a microphone which transmits the words into the line by means of the coils a a 0 c. The switch 15 is operated simultaneously with the switch 14 and serves to interpose the relay 11 12 in the current of the switchboard. It will be seen that the relay 11 12 enters into IIS operation only when the switch 14 of the telephone-receiver 5 has been openedthat is, when the subscriber alone speaks. Hence both microphones 7 and 11 cannot work simultaneously. The microphone current which comes from the subscribers line divides, so that it not only actuates the microphone 11 of the relay, but also passes over winding 6 through the separator; but it is to be observed with this that the portion of the current passing through the separator is so much weal:- ened by the large resistance which it encounters on its path that practically no counter disturbance of the two currents can be observed. The microphone and telephone must be isolated from all external noise.

WVhat I claim is 1. In a system of simultaneous telegraphy and telephony, the combination of a single circuit, telegraph instruments in said circuit, condensers between said circuit and the earth, a transformer havingcthree windings one of which is inserted in series with the main circuit, a microphone-circuit connected in series with another of the windings of the transformer, a closed circuit connected in series with the remaining winding of the transformer and divided into two branches, an iron core having the branches wound about it in opposite directions, and a telephone-receiver receiving the magnetic flux from the core.

2. In a combined telephone and telegraphic system, the combination with the main wire containing the telegraphic instruments, of a receiver-circuit, and a closed induction-circuit between the main wire and the receivercircuit receiving both the telegraphic and the telephonic frequencies provided with means for eliminating the telegraphic frequencies by causing the difference between the two frequencies to act on the receiver.

8. In acombined telephone and telegraphic system, the combination with the main wire containing the telegraphic instruments, of a closed induction-circuit receiving the impulses from the main wire and divided into two branches, a core having the branches wound about it in difierentdirections and atelephonereceiver receiving the magnetic flux from the core.

4. In a combined telephone and telegraphic system, the combination with the main wire containing the telegraphic instruments, of a receiver-circuit, and a closed induction-circuit between the main wire and the receivercircuit provided with means for eliminating the telegraphic frequencies, and a microphonecircuit connected with the main wire independently of the closed induction-circuit.

5. In a combined telephone and telegraphic system, the combination with the main wire containing the telegraphic instruments, of a receiver-circuit, and aclosed induction-circuit between the main wire and the receiver-circuit provided with means for eliminating the telegraphic frequencies, a microphone-circuit connected with the main wire independently of the closed induction-circuit, and a relay between the receiving-circuit and the microphone-circuit.

6. In a combined telegraph and telephone system, the combination with a single main wire, of telegraph instruments in circuit with the main wire, a winding in the main wire, a closed circuit having a winding adjacent the windin g of the main wire and divided into two branches, a core having the branches of the closed circuit wound about it in opposite directions, a receiver-circuit, and a winding in the receiver-circuit receiving the magnetic flux from the core of the closed circuit.

7. In a combined telegraph and telephone system, the combination with a single main wire, of telegraph instruments in circuit with the main wire, a winding in the main wire, a closed circuit having a winding adjacent the winding of the main wire and divided into two branches, a core having the branches of the closed circuit wound about it in opposite directions, a receiver-circuit, a winding in the receiver-circuit receiving the magnetic flux from the core of the closed circuit, a microphone-circuit, and a winding in the microphone-circuit adjacent the winding in the main wire.

8. In a combined telegraph and telephone system, the combination with a single main wire, of telegraph instruments in circuit with said main wire, a winding in the main wire, a closed circuit having a winding adjacent the winding of the main wire and divided into two branches, a core having the branches of the closed circuit wound about it in opposite directions, a receiver-circuit, a winding in the receiver-circuit receiving the magnetic flux from the core of the closed circuit, a microphone-circuit, a winding in the microphonecircuit adjacent the winding in the main wire,

and a relay between the receiver-circuit and the microphone-circuit.

9. In a system of simultaneous telegraphy and telephony, the combination of aline-wire, telegraph instruments connected with the linewire, condensers connecting the line-wire and a conductor, a receiver-circuit, a conductor interposed between the line-wire and the receiver-circuit divided into two branches, a core having the branches wound about it in opposite directions and from which the receiver-circuit receives magnetic flux, and a microphone circuit connected with the line-' wire independently of the two branches.

10. In a system of simultaneous telegraphy and telephony, the combination with a single line-wire containing the telegraphic instruments, a conductor divided into two branches and branched from the line-wire, a core having the branches of the branched conductor & 809,865

Wound about it in opposite directions, and a Wound diflerentially around acore from which 1 receivingcircuit receiving magnetic flux a telephone-receiver receives inductively the from the core. magnetic flux.

11. In asystem of simultaneous telegraphy Signed at 7577 Cornhill, London, E. (1., and telephony, the combination With the line- England, this 1st day of April, 1903.

Wire and its telephonic apparatus, of a cir- CARLO TURCHI. cuit connected at one end to the line, and at Witnesses: I

the other to the earth, divided intWo branches PERCY E. MATTOCKS each containing condensers and inductances, l

WM. 0. BROWN. 

